1. Field of the Invention
The present invention relates to an exposure technique that forms a pattern, which corresponds to a pattern formed in a mask, on an object and to a device fabrication technique that uses the exposure technique.
2. Related Art
Lithographic processes for fabricating devices (i.e., electronic devices and microdevices), such as semiconductor integrated circuits and liquid crystal display devices, conventionally use a full-field exposure type projection exposure apparatus, such as a stepper, to transfer a pattern formed in a reticle (or a photomask and the like) to each shot region on a wafer (or a glass plate and the like), which is coated with a resist, through a projection optical system.
To transfer the patterns of ever larger devices onto wafers without increasing the size of the projection optical system, scanning exposure type projection exposure apparatuses (scanning type exposure apparatuses), such as scanning steppers (scanners), have also been used in recent years (e.g., see Japanese Unexamined Patent Application Publication No. H04-277612); these projection exposure apparatuses scan the reticle and the wafer with respect to the projection optical system during the exposure using the projection magnification as a velocity ratio. In addition, to correct image forming characteristics, such as the field curvature of the projection optical system, an exposure apparatus is also known in the art (e.g., see Japanese Unexamined Patent Application Publication No. S61-232615) that simultaneously scans a pattern surface of a stationary reticle with a slit shaped illumination area and controls the positions (heights) of the reticle and the wafer in the optical axis direction of the projection optical system in accordance with the position of the illumination area.
To increase throughput in a scanning type exposure apparatus, it is necessary to increase the scanning velocities of the stages. Nevertheless, in a scanning type exposure apparatus, simply increasing the scanning velocities of the stages risks an increase in the size and complexity of the stage mechanisms, an increase in the magnitude of vibrations of the stages during the scanning exposure, and, as a result, a decrease in overlay accuracy and the like. In addition, during a regular scanning exposure, it is necessary to preserve a settling distance and a settling interval for each stage (the reticle stage and the wafer stage) that enable it to reach its constant velocity as determined by the projection magnification ratio. However, simply increasing the respective scanning velocities risks an increase in the respective settling distances and settling intervals, and consequently risks an increase in the exposure time.
In addition, a conventional exposure apparatus that controls the heights of the reticle and the wafer in accordance with the position of the illumination area does not particularly address ways to reduce the exposure time and thereby increase throughput.
A purpose of some aspect of the present invention is to provide an exposure technology that can improve the throughput of an exposing process without increasing the velocities of the stages, and a device fabrication technology that uses the exposure technology.